diff --git a/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiClient.java b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiClient.java
new file mode 100644
index 0000000..7f43d1f
--- /dev/null
+++ b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiClient.java
@@ -0,0 +1,61 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.gnmi.api;
+
+import com.google.common.annotations.Beta;
+
+import gnmi.Gnmi.CapabilityResponse;
+import gnmi.Gnmi.GetResponse;
+import gnmi.Gnmi.GetRequest;
+import gnmi.Gnmi.SetRequest;
+import gnmi.Gnmi.SetResponse;
+import org.onosproject.grpc.api.GrpcClient;
+
+import java.util.concurrent.CompletableFuture;
+
+/**
+ * Client to control a gNMI server.
+ */
+@Beta
+public interface GnmiClient extends GrpcClient {
+
+    /**
+     * Gets capability from a target. This allows device driver behavior
+     * to validate the service version and models which gNMI device supported.
+     *
+     * @return the capability response
+     */
+    CompletableFuture<CapabilityResponse> capability();
+
+    /**
+     * Retrieve a snapshot of data from the device.
+     *
+     * @param request the get request
+     * @return the snapshot of data from the device
+     */
+    CompletableFuture<GetResponse> get(GetRequest request);
+
+    /**
+     * Modifies the state of data on the device.
+     *
+     * @param request the set request
+     * @return the set result
+     */
+    CompletableFuture<SetResponse> set(SetRequest request);
+
+    // TODO: Support gNMI subscription
+}
diff --git a/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiClientKey.java b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiClientKey.java
new file mode 100644
index 0000000..26ce113
--- /dev/null
+++ b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiClientKey.java
@@ -0,0 +1,40 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.gnmi.api;
+
+import com.google.common.annotations.Beta;
+import org.onosproject.grpc.api.GrpcClientKey;
+import org.onosproject.net.DeviceId;
+
+/**
+ * Key that uniquely identifies a gNMI client.
+ */
+@Beta
+public class GnmiClientKey extends GrpcClientKey {
+
+    /**
+     * Creates a new gNMI client key.
+     *
+     * @param serviceName gNMI service name of the client
+     * @param deviceId    ONOS device ID
+     * @param serverAddr  gNMI server address
+     * @param serverPort  gNMI server port
+     */
+    public GnmiClientKey(String serviceName, DeviceId deviceId, String serverAddr, int serverPort) {
+        super(serviceName, deviceId, serverAddr, serverPort);
+    }
+}
diff --git a/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiController.java b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiController.java
new file mode 100644
index 0000000..f4964ed
--- /dev/null
+++ b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiController.java
@@ -0,0 +1,28 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.gnmi.api;
+
+import com.google.common.annotations.Beta;
+import org.onosproject.grpc.api.GrpcClientController;
+
+/**
+ * Controller of gNMI devices.
+ */
+@Beta
+public interface GnmiController
+        extends GrpcClientController<GnmiClientKey, GnmiClient> {
+}
diff --git a/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiEvent.java b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiEvent.java
new file mode 100644
index 0000000..5129926
--- /dev/null
+++ b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiEvent.java
@@ -0,0 +1,46 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.gnmi.api;
+
+import com.google.common.annotations.Beta;
+import org.onosproject.event.AbstractEvent;
+
+/**
+ * Representation of an event received from a gNMI device.
+ */
+@Beta
+public final class GnmiEvent extends AbstractEvent<GnmiEvent.Type, GnmiEventSubject> {
+
+    /**
+     * Type of gNMI event.
+     */
+    public enum Type {
+        /**
+         * Update.
+         */
+        UPDATE,
+
+        /**
+         * Sync response.
+         */
+        SYNC_RESPONSE
+    }
+
+    protected GnmiEvent(Type type, GnmiEventSubject subject) {
+        super(type, subject);
+    }
+}
diff --git a/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiEventListener.java b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiEventListener.java
new file mode 100644
index 0000000..0fe2fd3
--- /dev/null
+++ b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiEventListener.java
@@ -0,0 +1,27 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.gnmi.api;
+
+import com.google.common.annotations.Beta;
+import org.onosproject.event.EventListener;
+
+/**
+ * A listener of events received from gNMI devices.
+ */
+@Beta
+public interface GnmiEventListener extends EventListener<GnmiEvent> {
+}
diff --git a/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiEventSubject.java b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiEventSubject.java
new file mode 100644
index 0000000..d1563ed
--- /dev/null
+++ b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiEventSubject.java
@@ -0,0 +1,34 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.gnmi.api;
+
+import com.google.common.annotations.Beta;
+import org.onosproject.net.DeviceId;
+
+/**
+ * Information about an event generated by a gNMI device .
+ */
+@Beta
+public interface GnmiEventSubject {
+
+    /**
+     * Returns the deviceId associated to this subject.
+     *
+     * @return the device ID
+     */
+    DeviceId deviceId();
+}
diff --git a/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/package-info.java b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/package-info.java
new file mode 100644
index 0000000..5f07b46
--- /dev/null
+++ b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/package-info.java
@@ -0,0 +1,20 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * gNMI protocol API.
+ */
+package org.onosproject.gnmi.api;
\ No newline at end of file